The present invention relates to a heat exchanger having sheet-metal plates in spaced pairs, each pair having rail-like spacers positioned between laterally outer parallel longitudinal edges of the plates to keep them at a fixed distance from each other and for defining in each case a flat inner passage between the plates, the passage functioning as a conduit for a longitudinal flow of heat-exchange fluid, there being corrugated metal structures within said passage for increasing the heat-exchange surface area of the plates.
Prior-art heat exchangers of the character indicated are capable of being very simply produced, by sandwiched assembly of solder-coated sheet-metal plates with the rail-like spacers and with the corrugated metal structures, the sandwiched unit then being placed in a solder bath or in a soldering oven for bonded connection of the parts, that is to say, not only producing solder joints between the sheet metal plates and the outer-edge spacer rails (thereby determining, between each pair of plates, a fluid passage as a pipe of narrow cross-section), but also producing soldered connections at the points where the sheet metal plates are contacted by the corrugated structures within the passage. In prior-art heat exchangers, such corrugated structures have been produced in the form of thin corrugated metal strips or sheets somewhat like corrugated iron, there then being solder-fixed joints at outer limits of the folds in the corrugated strips or corrugated sheets.
Heat exchangers thus far produced along the indicated lines generally provide a first set of flat passages for the flow of a first fluid and a second set of flat passages for the flow of a second fluid. Generally, the flat fluid passages of one set are spaced by the flat fluid passages of the other set. In application as an air-oil heat exchanger for cooling purposes, one of the fluids is oil, under an elevated pressure, and the other of the fluids is air for cooling the oil. In application as a heat exchanger for an air compressor, both fluids are air. In such applications, very high pressure differences are likely between the cooling air, normally at atmospheric pressure, and the pressurized oil or air to be cooled. More specifically, in the case of an air/air heat exchanger for cooling in connection with a high-pressure compressor, or in the case of an air/oil heat exchanger for cooling a hydraulic system, the involved high pressure differences may not be safely contained in prior-art heat exchangers of the character indicated, so that in use, such heat exchangers may be unsafe.